diff --git a/app/models/Client.scala b/app/models/Client.scala
index ffa995b..34b399e 100644
--- a/app/models/Client.scala
+++ b/app/models/Client.scala
@@ -22,5 +22,5 @@ class Client(val path: File) {
     process
   }
 
-  def destroy(): Unit = if (process == null) process.destroy
+  def destroy(): Unit = if (process != null) process.destroy
 }
diff --git a/app/models/ProgramThread.scala b/app/models/ProgramThread.scala
new file mode 100644
index 0000000..861681e
--- /dev/null
+++ b/app/models/ProgramThread.scala
@@ -0,0 +1,35 @@
+package models
+
+import java.io.{InputStreamReader, BufferedReader}
+
+class ProgramThread(builder: ProcessBuilder) extends Thread {
+  private var process: Process = null
+  private val stringBuilder = new StringBuilder()
+  private var callback: Option[String => Unit] = None
+
+  def setCallback(acb: String => Unit) = callback = Some(acb)
+
+  override def run() = {
+    process = builder.start
+    val streamReader = new InputStreamReader(process.getInputStream)
+    val bufferedReader = new BufferedReader(streamReader, 1)
+    var line:String = null
+
+    while({line = bufferedReader.readLine; line != null}){
+      stringBuilder.append(line)
+      stringBuilder.append("\n")
+      callback.map(_(line))
+    }
+    bufferedReader.close
+
+    process.waitFor
+  }
+
+  def waitFor: Unit = if (process != null) process.waitFor
+
+  def forceExit: Unit = if (process != null) process.destroy
+
+  def getOutput: String = stringBuilder.toString
+
+  def exitValue: Int = process.exitValue
+}
diff --git a/app/models/Server.scala b/app/models/Server.scala
index 5e4547e..6ec14a6 100644
--- a/app/models/Server.scala
+++ b/app/models/Server.scala
@@ -1,6 +1,6 @@
 package models
 
-import java.io.{File, InputStreamReader, BufferedReader}
+import java.io.{File}
 import play.Logger
 
 /**
@@ -20,40 +20,33 @@ extends Thread {
   override def run() = {
     val builder = new ProcessBuilder(SERVER_PROGRAM.toString,
       "-p", port.toString, "-t", ROUND_TIMEOUT.toString)
-    val stringBuilder = new StringBuilder()
     builder redirectErrorStream true
     builder directory SERVER_PROGRAM.getParentFile
 
     try {
-      val proc = builder.start
-      val streamReader = new InputStreamReader(proc.getInputStream)
-      val bufferedReader = new BufferedReader(streamReader, 1)
-      var line:String = null
-      var char: Int = 0
-
-      challenger.run(port)
-
-      while({line = bufferedReader.readLine; line != null}){
-        stringBuilder.append(line)
-        stringBuilder.append("\n")
+      val pt = new ProgramThread(builder)
+      pt.setCallback { line =>
+        if (line == "Waiting connections ... ") {
+          println("invoking")
+          challenger.run(port)
+          Logger.info("challenger's client is started")
+        }
         if (line == "One player is registered. Waiting for other player ...") {
           opponent.run(port)
           Logger.info("opponent's client is started")
         }
       }
-      bufferedReader.close
-
-      val result = stringBuilder.toString
 
-      proc.waitFor
+      pt.start
+      pt.join
 
       challenger.destroy()
       opponent.destroy()
 
-      if (proc.exitValue == 0) {
-        BattleRecorder.report(NormalExit(battle, result))
+      if (pt.exitValue == 0) {
+        BattleRecorder.report(NormalExit(battle, pt.getOutput))
       } else {
-        BattleRecorder.report(AbnormalExit(battle, result))
+        BattleRecorder.report(AbnormalExit(battle, pt.getOutput))
       }
     } catch {
       case e: Exception =>